Denver Mint correspondence scanned at the National Archives (NARA) in Denver - covering the period 1897-1994. NARA identifier is record group 104, 8NS-104-94-077. Box 1, Folder 17. Folder 17 title: “... Letters Pertaining to Approx 1906.” Courtesy of John Graffeo.
While some of the folders in this respective sequence may be numbered and others may not be - new numbers were assigned to each folder based on the archival theory of original order - which is strongly respected and maintained by NARA. These new numbers are represented in the metadata, and again - they represent the order in which the folders were found in the archival boxes to which they belong.